The Leinster centres both picked up hamstring injuries in Ireland's 28-17 win in Italy last weekend and captain O'Driscoll was ruled out on Thursday night while D'Arcy failed a fitness test on Friday morning.

As a result, O'Sullivan believes the Scots' chances of causing an upset have now improved dramatically.

He said: ''We have two world-class centres of the calibre of ODriscoll and D'Arcy and we are missing both of them.

''I think we have managed to hang onto one of them for every game in the last five but now we've got to deal with both out.

''It's a fairly serious setback and it's not what we were looking for but at the same time we knew this was a possibility almost a week ago and we've been working around it.

''But if people are talking us up with regards us being favourites, then this does level the playing field.

''I think it's going to be a very tight game and if it wasn't going to be before, then it is going to be tight now.''

O'Sullivan denied any psychological plan to confuse the Scots was behind his reluctance to rule out both players straight after the Italy match.

He said: ''If you were in my shoes you would give them every possibility wouldn't you? That's what I did.

''At the start of the week there was a chance and we had to play it out. It would be foolish man who ruled them out on Monday morning to find they were on the pitch today.

''It was obvious Brian wasn't as far on as Gordon by Thursday and we said we would give it until Friday.

''Gordon wasn't far away but considering this is only our second game of the championship and there are still three to go after that. It was sensible caution.''